In general, a display device refers to monitors for a TV or a computer as a whole, and comprises a display diode forming an image and a case supporting the display diode.
Examples of the display diode may comprise a plasma display panel (PDP), a liquid crystal display (LCD), an electrophoretic display, a cathode-ray tube (CRT), an OLED display and the like. An RGB pixel pattern for implementing an image and an additional optical filter may be provided in the display diode.
Meanwhile, relating to a display device, as the spread of smart phones, tablet PCs, and IPTVs is accelerated, a demand for a touch function that uses human hands as a direct input device without a separate input device such as keyboards or remote controllers is growing. In addition, a multi-touch function for recognizing a specific point and taking notes is also required.
The touch screen that performs the aforementioned function may be classified into the following types according to a detection manner of a signal.
That is, there are a resistive type detecting a position pressed by pressure in a state where a direct voltage is applied through a change in current or voltage value, a capacitance type using capacitance coupling in a state where an alternating voltage is applied, an electromagnetic type detecting a selected position in a state where a magnetic field is applied as a change in voltage and the like.
Among them, the resistive type and capacitance type touch screens that are most extensively spread recognize the touch by a change in electric contact or capacitance by using the transparent conducting film such as the ITO film. However, since most of the transparent conducting films has high resistance of 150 ohm/square or more, sensitivity is reduced in enlargement, and when the touch screen is manufactured by using the same, there are a complexity that a patterning process of ITO and a patterning process of an electrode of a metal trace portion are sequentially performed by a process such as photolithography and a problem that a cost of an ITO film is rapidly increased as a size of a screen is increased, such that there are an increase in manufacturing cost and difficulty in application to enlargement while manufacturing is performed. In order to overcome this, currently, there is an effort to implement enlargement by using a metal pattern having the high conductivity. In the case where the metal pattern is used, the metal pattern is useful to area enlargement due to high conductivity of the metal, and is advantageous in view of yield and cost because the trace electrode and the image portion are formed simultaneously to reduce the number of processes.
However, in the case where the touch screen is constituted by using the metal pattern, additional optical phenomena occur due to structural characteristics different from those of a known ITO, one of them is a reflective diffraction phenomenon by a point light source such as sunlight, and another is a moiré phenomenon exhibited when a regularized metal pattern is used.
In this case, the reflective diffraction phenomenon means that when the point light source such as sunlight or interior LED radiates light on a surface where the metal pattern of the display is provided, in the case where the metal pattern is regular, a pattern is formed by forming diffraction by reflection of the point light source, reducing legibility of a user. The reflective diffraction phenomenon is being magnified as an optical property to be even more managed because adoption of lightweight and portable products is gradually increased in current displays to emphasize outdoor visibility and the like.
Separately, the moiré phenomenon is a phenomenon where another type of interference pattern is formed due to an interference phenomenon between the pixel and the pattern of the display in the case where a regular pattern is present on a pixel pattern or an electrode pattern of the display, and this phenomenon reduces legibility and disturbs mixing of colors of the pixel to cause a problem of reducing an image quality of the display.
In the case of a plasma display panel (PDP) as an example thereof, in the case where a metal mesh pattern for blocking electromagnetic waves is introduced, a moiré phenomenon may occur due to regularity of the pixel and the metal mesh pattern of the plasma display. Therefore, in order to solve this, in general, if the specification of the plasma display panel (PDP) is determined, an effort for solving the moiré phenomenon is made through an angle design of a metal mesh pattern of an optical filter.
However, avoidance of the moiré phenomenon through setting of the angle of the display pixel and the metal mesh pattern is cumbersome in that different patterns need to be used according to the size of the display and the pixel implementation manner.